1. Technical Field
The present invention generally relates to a device for forming optical lenses, particularly, to a device for forming optical lenses for producing optical lenses.
2. Discussion of Related Art
With continuous development of multimedia technology, electronic devices such as digital cameras, digital camcorders, and mobile phones having camera module are becoming more and more popular. These electronic devices are required to be small in size and provide good image quality Lens employed in these products play an important role in obtaining a good image quality.
Typically, a lens module includes a plurality of lenses, optical filters and an image sensor. Lenses are usually made of glass or transparent plastic material. Glass lenses are generally made by mold pressing, and plastic lenses are generally made by injection molding.
However, lenses made by injection molding may subject to internal stress caused by process conditions, such as injection rate, injection pressure and injection time. The internal stress may cause deformation of the lenses thus, deteriorates optical performance of the lenses. For example, refractive index of the lenses may be deflected. Referring to IEEE, International Symposium on Polarization Analysis and Applications to Device Technology, 1996, “Dynamic variation of internal stress distribution in the curing process of epoxy resin using highly sensitive birefringence measurement system”, Shigekazu Yamagishi also discloses how internal stress influence lenses' optical performance.
Therefore, there is a desire to develop a device for producing lenses with reduced internal stress.